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javaweb 封装(增,删,改,查)

墨香子儿 2022-04-05 阅读 65
java

dao方法: 

package com.ruojuan.Dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import com.ruojuan.entity.News;
import com.ruojuan.util.DBHelper;

/**
 * 新闻的增删改查
 * @author 刘若娟
 *
 * 2022年4月5日下午5:39:06
 */



public class NewsDao {
	//扩大作用域
	//三兄弟
	private Connection con = null;
	private PreparedStatement ps = null;
	private ResultSet rs = null;
	
	/**
	 * 查询新闻的id 标题,作者
	 * @return 新闻的集合
	 * 
	 */
	public List<News> getAll(){
		List<News> ls=new ArrayList<News>();
		try {
			//创建连接
	      	con=DBHelper.getCon();
	      	//定义sql语句
	      	String sql="select nid,ntitle,nauthor from news280 order by nid desc";
	      	//获得执行对象
	      	ps=con.prepareStatement(sql);
	      	//获得结果集
	      	rs=ps.executeQuery();
	      	//循环遍历
	      	while(rs.next()){
	      		//实例化新闻对象
	      		News n=new News();
	      		//给对象赋值
	      		n.setNid(rs.getInt(1));
	      		n.setNtitle(rs.getString(2));
	      		n.setNauthor(rs.getString(3));
	      		//加到集合中
	      		ls.add(n);
	      	}
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBHelper.myClose(con, ps, rs);
		}
		return ls;
	}
	
	
	//增加新闻
	public int addNew(News ns) {
		int n = 0;
		try {
			con = DBHelper.getCon();
		 	 String sql="select nvl(max(nid),0) from tb_news";
		 	 //out.print(sql);
		 	 //获得执行对象
		 	 ps=con.prepareStatement(sql);
		 	 //获得结果集
		 	 rs=ps.executeQuery();
		 	 //扩大作用域
		 	 int nid = 0;
		 	 //判断
		 	 if(rs.next()){
		 		 //最大序号+1
		 		 nid = rs.getInt(1)+1;
		 	 }
		 	 //实现增加=插入操作
		 	 sql = "insert into tb_news(nid,tid,ntitle,nauthor,nsummary,ncontent,naddtime) values(?,?,?,?,?,?,?)";
			 //执行sql语句
			 ps = con.prepareStatement(sql);
			 //给占位符赋值
			 ps.setInt(1, ns.getNid());
			 ps.setInt(2, ns.getTid());
			 ps.setString(3,ns.getNtitle());
			 ps.setString(4, ns.getNauthor());
			 ps.setString(5, ns.getNsummary());
			 ps.setString(6, ns.getNcontent());
			 ps.setString(7, ns.getNaddtime());
			 
			 //获得影响行数
			 n = ps.executeUpdate();
	
		}catch(Exception e){
			e.printStackTrace();
		}finally {
			DBHelper.myClose(con, ps, null);
		}
		return n;
	}
	
	
	//删除新闻
	public int deleteNew(int nid) {
		int n = 0;
		try {
			con = DBHelper.getCon();
			 String sql="delete from tb_news where nid="+nid;
			 //获得执行对象
			 ps=con.prepareStatement(sql);
			 //给占位符赋值
			 ps.setInt(1, nid);
			 //开始执行
			 n=ps.executeUpdate();//影响行数
			 
		} catch (Exception e) {
			// TODO: handle exception
		}finally {
			DBHelper.myClose(con, ps, null);
		}
		return n;
	}
	
	//修改新闻
	public int updateNew(News ns,int nid) {
		int n = 0;
		try {
			con = DBHelper.getCon();
			String sql="update tb_news set tid=?,ntitle=?,nauthor=?,nsummary=?,ncontent=?,naddtime=? where nid=?";
			ps=con.prepareStatement(sql);
			//给占位符赋值
			ps.setInt(1, ns.getTid());
			ps.setString(2, ns.getNtitle());
			ps.setString(3, ns.getNauthor());
			ps.setString(4, ns.getNsummary());
			ps.setString(5, ns.getNcontent());
			ps.setString(6, ns.getNaddtime());
			ps.setInt(7, nid);
			
			//获得影响行数
			n = ps.executeUpdate();

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			DBHelper.myClose(con, ps, null);
		}
		
		return n;
	}
	
	
	
	
	
}

增加:

增加的逻辑处理页面:

 

删除:

删除的逻辑处理页面:

 

修改:

修改的逻辑处理页面:

 

查看:

查看的逻辑处理页面:

 

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